The present invention is a method for efficiently manufacturing a polymer having hydrocarbon oxysilyl groups from a hydride (hydrocarbonoxy)silane compound and an unsaturated polymer having olefin or acetylene groups.
Alkoxysilyl modified silicones, alkoxysilyl functional polyolefins, and other such polymers having hydrocarbon oxysilyl groups are materials that have important industrial applications, such as the improvement of surface adhesion between a silanol produced by hydrolysis and a solid surface through the reaction or interaction of the polar groups thereon, or curing by the formation of crosslinks between polymer chains by the formation of siloxane bonds as a result of the hydrolysis of silyl groups and subsequent dehydration/condensation.
A polymer having alkoxysilyl groups, which are typical hydrocarbonoxysilyl groups, can be manufactured by methods broadly classified into the following two groups. The first method involves copolymerizing the monomer that is the principal raw material of the polymer with a comonomer having alkoxysilyl groups on a portion thereof, with a hydro-crosslinkable polyolefin being an example of the polymer that is obtained. A reactive comonomer having alkoxysilyl groups is essential in conducting this method. Also, since alkoxysilyl groups are generally highly reactive and susceptible to hydrolysis, limits are imposed on the reaction conditions, and not all polymers can be used with this method.
The second method involves the hydrosilylation reaction of a polymer having olefinic or acetylenic unsaturated groups with a hydride alkoxysilane compound. Specific examples include the introduction of alkoxysilyl functional groups into a double-terminated vinyl functional polydimethylsiloxane through a hydrosilylation reaction using a trialkoxysilane (U.S. Pat. No. 4,599,394); the introduction of trialkoxysilyl functional groups into a double-terminated allyl functional polyisobutylene through a hydrosilylation reaction using a trialkoxysilane (Japanese Laid-Open Patent Application 63-6041); and the introduction of dialkoxysilyl functional groups into a double-terminated allyl functional polyethylene glycol through a hydrosilylation reaction using a methyldialkoxysilane (Japanese Laid-Open Patent Application 57-190043). However, because the unsaturated group concentration in these polymers was low and the reaction was slow, the above reactions generally had to be conducted by using a large excess of hydroalkoxysilane compound and a large amount of hydrosilylation catalyst. Also, oxygen frequently had to be added to the reaction atmosphere during the hydrosilylation reaction in order for catalytic activity to be manifested and sustained. The addition of oxygen was attended by the danger of ignition and explosion.
An object of the present invention is to provide a novel method for manufacturing a polymer having hydrocarbonoxysilyl groups through a hydrosilylation reaction using a hydride (hydrocarbonoxy)silane compound, which method has a wider range of applicability and a simpler procedure than the above two methods. Specifically, the present invention provides a method where the proportion of hydrocarbonoxysilyl groups that are bonded to primary carbons of the polymer can be raised and the proportion of those bonded to secondary carbons can be lowered by an improvement to the selectivity of the addition position in the hydrosilylation reaction, and which thus makes it possible to obtain a polymer that is more readily hydrolyzed and that contains more hydrocarbon oxysilyl groups. The present invention also provides a method with which a platinum catalyst is more highly activated and the activity thereof is sustained better, which makes it possible to perform the hydrosilylation reaction more economically and to carry out this reaction at a lower oxygen partial pressure or in an inert atmosphere, and thus allows the danger of ignition or explosion to be reduced during the hydrosilylation reaction.
Specifically, an object of the present invention is to provide a method where, in the introduction of hydrocarbon oxysilyl groups into a polymer through a hydrosilylation reaction between a hydride (hydrocarbonoxy)silane compound and unsaturated groups bonded to the polymer, (1) the activity of a platinum catalyst can be raised, the activity sustained longer, and the catalyst costs reduced; (2) the position selectivity in the reaction can be enhanced, and the hydrocarbonoxysilyl groups that are bonded to the primary carbons of the polymer can thus be provided more selectively; and (3) the hydrosilylation reaction can be carried out at a lower oxygen partial pressure or in an inert atmosphere, and thus the danger of ignition or explosion during the hydrosilylation reaction can be reduced.
The inventors discovered that catalytic activity, how long this activity is sustained, and reaction selectivity can be greatly improved and a hydrosilylation reaction can be accomplished quickly in the absence of oxygen or at a low oxygen partial pressure by having a small amount of carboxylic acid compound be present in the reaction system in the course of adding a hydride (hydrocarbonoxy)silane compound, whose reactivity is low when used alone, to an olefinic or acetylenic functional polymer in a hydrosilylation reaction in which a platinum catalyst is used.